The primary use of an electrical power supply network is to distribute energy to consumers. Notwithstanding this primary purpose, an electrical power distribution network can be used with advantage to transmit frequencies other than the fundamental power frequency for data purposes.
One system for accomplishing such data transmission is disclosed in an article entitled "Data Transmission over Distribution Systems" by A. J. Baggott, Electrical Times Mar. 12, 1970. The power transmission frequency of the distribution network is used as the carrier waveform. Information signals are encoded on the carrier by selectively distorting the carrier waveform.
The distortions of the carrier waveform are formed by using a thyristor to switch a resistive, capacitative, or inductive load between two power lines. The system for transmitting data described in the aforementioned article is particularly adapted to transmit such data in the direction of energy flow in the power supply network.
A similar system for the transmission of data in an electrical supply network is disclosed in Swiss Patent No. 404,775. In the system of Swiss Patent No. 404,775, data is transmitted in a direction counter to that of the energy flow. The data carrying signals are generated by switching a capacitative load between two power lines.
It is an object of the present invention to provide an improved method for forming and transmitting information carrying signals in an electric power distribution network, which method would:
(a) involve the use of simple and inexpensive electrical components, PA0 (b) produce information carrying signals of low harmonic content, so that requirements relating to cross-talk are easily met, and PA0 (c) offer improved energy exploitation, and PA0 (d) economize costs.